Composite parts make it possible to contribute to the lightening of motor vehicle structures.
It is known, in particular from the patent FR 2 866 592, to manufacture, for this purpose, a part comprising a sheet of steel covered with one or more adherent films of polymer with a thickness of at least 0.1 millimeter. This part, basically in the coil form, has to be able to withstand all the processing stages (handling, cutting, bending, embossing, piercing, and the like).